The present invention relates generally to phased array antenna systems and specifically to a portable test system and technique to determine the operational status of phase control modules (PCM) within a phased array antenna.
Phased array antennas that can be steered electronically are finding increasing applications in both radar and communication systems. In radar, the electronically steerable phased array antenna appears to be the best way to track or search many targets widely separated in space. An electronically steered phased array antenna can slew rapidly on a pulse-to-pulse basis throughout the entire azimuth and elevation region accessible to the radar, leading to multiple-target tracking capability. For communications, phased array antennas provide the maximum practical gain over other steerable antennas which suffer from limitations imposed by stress capabilities and manufacturing tolerances in materials. The gain which can be achieved by electronically steerable phased array radar antennas is limited only by the amount of land available and by dispersion along the propagation path. Phased array radar systems offer many advantages over mechanically swept antennas, the most notable being their ability to select a given azimuth and elevation pointing angle without physically moving the antenna.
A problem with phased array antennas is the testing of the phase control modules may be construed as element drivers power and phase control and amplification in the array. Remote radar systems are not easily transported back to a test facility. The task of remotely testing phased array antennas is alleviated, to some degree, by the following U.S. Patents, which are incorporated herein by reference.
U.S. Pat. No. 3,378,846 issued to Lowenschuss on 16 Apr. 1968;
U.S. Pat. No. 4,128,812 issued to Pavlis on 5 Dec. 1978;
U.S. Pat. No. 4,424,483 issued to Aslan on 3 Jan. 1984;
U.S. Pat. No. 4,434,397 issued to Nelson on 28 February 1984; and
U.S. Pat. No. 4,453,164 issued to Patton on 5 June 1984.
Lowenschuss is directed to a method and apparatus for testing the individual elements and phase shifters of a phased array antenna. A reference signal is supplied to the array from a continuous wave (CW) source and test antenna. The array is steered by phase shifters receiving array control command signals from an array control command circuit. Phase shifters are varied one at a time in a prescribed manner by the array control commands. A large radiator picks up signals from the antenna radiators and supplies them to a receiver for processing.
Aslan shows a portable instrument for monitoring the power density of a microwave field. The device of this patent includes a probe which carries a spiral antenna. Patton uses near field data to correct the phase of individual elements of a phased array antenna. Nelson discloses an adaptive technique for monitoring the individual currents in a phased array antenna system. Pavlis discusses a phase discriminator for indicating when a signal is either in phase with a reference signal or alternately 180 degrees out of phase with a reference signal.
The task of transporting elaborate and cumbersome test equipment to an antenna can prove as trying as transporting the antenna itself to a test facility. From the foregoing discussion, it is apparent that there currently exists a need for a portable phase shifter (or radiating element) testing system. The present invention is intended to satisfy that need.